当表中一个主键不能唯一标识一条记录的时候，就需要使用联合主键了，下面是使用JPA注解实现联合主键的代码

1 首先需要建立一个复合主键类，用来存放需要生产联合主键的属性，该类需要实现序列化。

package com.ericsson.adp.entity.cons;

import java.io.Serializable;

public class ConsumerGroupMapPK implements Serializable{

    private String msisdn;//电话号码

    private Long tagGroupId;//(10)标签组id

    public String getMsisdn() {

       return msisdn;

    }

    public void setMsisdn(String msisdn) {

       this.msisdn = msisdn;

    }

    public Long getTagGroupId() {

       return tagGroupId;

    }

    public void setTagGroupId(Long tagGroupId) {

       this.tagGroupId = tagGroupId;

    }

}

然后再写一个类，该类对应数据库中的表，在该类中需要使用@IdClass(ConsumerGroupMapPK.class)引入上面写的复合主键类

同时在需要做成联合主键的属性上面加上@Id标明该属性是主键就好了

package com.ericsson.adp.entity.cons;

import javax.persistence.EmbeddedId;

import javax.persistence.Entity;

import javax.persistence.Id;

import javax.persistence.IdClass;

import javax.persistence.Table;

import org.hibernate.annotations.Cache;

import org.hibernate.annotations.CacheConcurrencyStrategy;

@Entity

@IdClass(ConsumerGroupMapPK.class)

@Table(name="T_CONS_CONSUMER_GROUP_MAP")

@Cache(usage=CacheConcurrencyStrategy.READ_WRITE)

public class ConsumerGroupMap{

    @Id

    private String msisdn;//电话号码

    @Id

    private Long tagGroupId;//(10)标签组id

    public ConsumerGroupMap() {

       super();

       // TODO Auto-generated constructor stub

    }

    public ConsumerGroupMap(String msisdn, Long tagGroupId) {

       super();

       this.msisdn = msisdn;

       this.tagGroupId = tagGroupId;

    }

    public String getMsisdn() {

       return msisdn;

    }

    public void setMsisdn(String msisdn) {

       this.msisdn = msisdn;

    }

    public Long getTagGroupId() {

       return tagGroupId;

    }

    public void setTagGroupId(Long tagGroupId) {

       this.tagGroupId = tagGroupId;

    }

}